Quantitative analysis of trivalent uranium and lanthanides in a molten chloride by absorption spectrophotometry

As an analytical application for pyrochemical reprocessing using molten salts, quantitative analysis of uranium and lanthanides by UV/Vis/NIR absorption spectrophotometry was performed. Electronic absorption spectra of LiCl–KCl eutectic at 773 K including trivalent uranium and eight rare earth elements (Y, La, Ce, Pr, Nd, Sm, Eu, and Gd as fission product elements) were measured in the wavenumber region of 4,500–33,000 cm^?1. The composition of the solutes was simulated for a reductive extraction condition in a pyroreprocessing process for spent nuclear fuels, that is, about 2 wt% U and 0.1–2 wt% rare earth elements. Since U(III) possesses strong absorption bands due to f–d transitions, an optical quartz cell with short light path length of 1 mm was adopted in the analysis. The quantitative analysis of trivalent U, Nd, Pr, and Sm was possible with their f–f transition intensities in the NIR region. The analytical results agree with the prepared concentrations within 2σ experimental uncertainties.     

Extraction of uranium(VI) from nitric acid solution by N,N-dibutyldodecanamide

The partition of uranium(VI) between nitric acid solutions and solutions of N,N-dibutyldodecanamide (DBDA) in kerosene has been investigated at varying concentrations of nitric acid, extractant, salting-out agent LiNO₃ and at different temperatures. The mechanism of extraction is discussed in the light of the results obtained.     

The determination of uranium isotopes by atomic absorption spectrophotometry

The uranium isotopes, ²³⁵U and ²³⁸U, can be determined easily by atomic absorption techniques, employing relatively inexpensive and unsophisticated equipment. A water-cooled hollow-cathode discharge tube was used as an absorption tube. It was found that large amounts of uranium atoms, in the ground state, were produced by the discharge in the tube. Thus the inherently weak uranium resonance radiation coming from. an emission source and passing through the absorption tube was absorbed. For the first time in an atomic absorption technique, samples and related standards were used in the emission source instead of an absorption source, and a high degree of accuracy and precision was obtained. Valid results were also obtained by conventional techniques — that is, the samples and related standards were employed in the absorption source.     

Determination of platinum, palladium, and gold in a silver assay bead by atomic absorption spectrophotometry

Summary A procedure is given for the atomic absorption determination of platinum, palladium and gold in silver beads. Interferences by coexisting ions usually found in the parting solution could be eliminated by addition of 1% of lanthanum. The lowest working ranges in which it is possible to obtain results comparable in accuracy to those from a good spectrophotometric determination are estimated for each metal. (1 ppm Pd, 1 ppm Au, 5 ppm Pt). The results of several determinations using the proposed procedure to analyse silver assay beads are given.

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Bestimmung von Platin, Palladium und Gold in dokimastischen Silberperlen durch Atomabsorptions-Spektrophotometrie

Zusammenfassung Störungen durch in der Scheidelösung vorhandene Begleitionen konnten durch Zusatz von 1% Lanthan verhindert werden. Die unteren Grenzen für eine genaue Bestimmbarkeit wurden festgelegt (1 ppm Pd, 1 ppm Au, 5 ppm Pt) und Ergebnisse mehrerer Beleganalysen mitgeteilt.

     

Conductometric determination of carbon in uranium carbide and its solution in nitric acid

A simple but accurate method has been developed for the determination of carbon in uranium carbide powders/pellets as well as in solutions of uranyl nitrates. The methodology involves quantitative conversion of carbon present in the sample to carbon dioxide that is subsequently absorbed in a dilute solution of barium hydroxide. The conductivity shift of the barium hydroxide solution is monitored on-line continuously using a laboratory-built PC-based conductivity measurement system that has been developed in-house based on the direct conversion of conductance to the digital pulse frequency. A new gas absorption cell has been designed to ensure quantitative absorption during the residence time of the gas in the cell. The method is sensitive, accurate and precise to 1-3% at 600-1000 mug of carbon in samples of uranium carbide.     

Extraction of nitric acid,technetium and palladium by bidentate carbamoylphosphonates

The extraction of HNO₃, TcO ₄ ^? , and Pd by solutions of dibutyl N,N-diethylcarbamoylmethylenephosphonate (DBDECMP) and dibutyl N,N-diethylcarbamoylphosphonate (DBDECP) in CCl₄ has been studied. At low aqueous acidities, HNO₃ is extracted by both extractants (S) as HNO₃·S and HNO₃·S₂, at >1M HNO₃ only HNO₃·S is formed. The distribution of TcO ₄ ^? and Pd(II) is nearly independent of HNO₃ concentration. A second power dependence on extractant concentration was found for the extraction of Pd(II) by DBDECMP and TcO ₄ ^? by DBDECP, and a 4th power dependence for TcO ₄ ^? -DBDECMP.     

Electronic absorption spectra of palladium(II) in concentrated nitric acid solutions

Palladium complexation in concentrated nitric acid solutions was studied by UV/Vis absorption spectrophotometry. The ionic strength of the solutions was fixed to I = 1, 3, or 5 mol dm⁻³ (M) by mixing of HNO₃ and HClO₄. The major palladium species were found to be Pd²⁺, PdNO₃ ⁺, and Pd(NO₃)₂. The formation constant of PdNO₃ ⁺ was determined to be β ₁ = 1.32 (I = 1 M), 1.49 (I = 3 M), or 1.47 (I = 5 M), while that of Pd(NO₃)₂ to be β ₂ = 0.45 (I = 3 M) or 0.14 (I = 5 M).     

Thermodynamics of uranium extraction from nitric acid solution by TBP loaded on inert supporting material

Thermodynamic investigation of the extraction of both uranium(VI) and uranium(IV) from nitric acid solutions using tri-n-butyl phosphate (TBP) loaded on polyacrylic acid polymer (SM-7) as an inert supporting material has been done using batch technique. The effect of temperature on the equilibrium extraction values has been utilized to evaluate the change in standard thermodynamic quantities (viz. DH, DS, and DG). The Freundlich isotherm was successfully applied to the extraction data of both metal ions. The Dubinin-Radushkevich (D-R) isotherm was found to be valid only in case of U(IV) extraction. Based on the D-R expression, the maximum extraction capacity of loaded TBP and the mean free energy of U(IV) extraction have been determined.     

钯与对若丹宁偶氮苯甲酸络合物的固相萃取和光度测定

根据新试剂对若丹宁偶氮苯甲酸(RABA)与钯的显色反应及C18固相萃取小柱对显色络合物的固相萃取,建立了一种测定痕量钯的新方法,在pH为2.0～4.0的HCl-邻苯二甲酸氢钾(HCl-KHP)缓冲介质中,在CTMAB存在下,钯与RABA发生反应形成1:1的稳定络合物,该络合物可用C18固相萃取小柱富集,小柱上富集的络合物用乙醇洗脱后用光度法测定,在富集后的测定液中,络合物最大吸收波长为500 nm,摩尔吸光系数ε=1.36×105 L·mol-1·cm-1,Pd2 量在0.1～1.0 μg/mL内符合比尔定律,方法用于催化剂中钯的测定.     

Determination of platinum and palladium in strongly acid solution by means of flow injection analysis

Microamounts of Pt(II/IV) (0.25–800 μg/ml) and Pd(II) (5–600 μg/ml) in> 0.5 M hydrochloric acid can readily be determined by means of a simple FIA method based on the selective reaction of tin(II)chloride with these metals. The FIA method has a high linear dynamic range, and is relatively free from interferences of many transition metals, with the exception of Au and Rh; small amounts of other PGMs can be tolerated. Determination of Pt on a hydrogenation catalyst by this method compares well with that found by flame atomic absorption spectroscopy. By monitoring at two or more wavelengths, Pt and Pd can be determined in mixtures by this means, to yield a simple, cost-effective FIA method for possible on-line determinations and quality control of, in particular, Pt containing acidic refinery and other process streams.     

Extraction of uranium(VI) and thorium(IV) from nitric acid solution by N-alkylcaprolactam

Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous NHO₃ concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions.     

Kinetic studies on the oxidation of uranium(IV) in nitric acid solution

The kinetics of oxidation of U(IV) in nitric acid solution by nitrous acid and air oxygen have been studied. The effects of concentrations of U(IV), nitric acid, hydrogen ion and nitrous acid in aqueous solution or oxygen in gas on the oxidation rate have been examined. The oxidation rate increases with increasing temperature and the activation energies are 47 kJ mol^–1 for nitrous acid and 91 kJ mol^–1 for oxygen. The mechanisms for both oxidation reactions are discussed.     

Quantitative determination of vitamin b12 by cyan dosage,with infrared absorption spectrophotometry

Microchimica Acta - Vitamin B12 has been determined by measurement of the infrared absorption of the cyano-group band at 2137 cm?1, the samples being pelleted with KBr. The error is within...     

Preparation of uranium(III) by mercury cathode electrolysis and its absorption spectra in hydrochloric acid solution

The reduction of hexavalent to trivalent uranium by mercury cathode electrolysis in hydrochloric acid solution was investigated. The dependence of the reducton ratio on the different media, the acid and uranium concentrations, and on the time of electrolysis was determined. It was found that hexavalent uranium can be reduced quantitatively to trivalent state by mercury cathode electrolysis. The absorption spectra of U(III) and U(IV) in 1M and 9M hydrochloric acid solutions were examined. The molar extinction coefficient of U(III) at 521 nm was 16.7 m²·mol^–1 within the HCl concentration range of 0.5–4.5M. U(IV) practically does not interfere in the photometric determination of U(III) at this wavelength. A good linear dependence of absorbance on the concentration of U(III) was found.     

Simultaneous spectrophotometric determination of uranium, nitric acid and nitrous acid by least-squares method in PUREX process

Multi-wavelength linear regression spectrophotometry combined with method of least squares for simultaneous determination of uranium, nitric acid and nitrous acid in PUREX (Plutonium/URanium EXtraction) process was developed. The molar absorbance matrix was calibrated with absorbance data measured in the wavelength range of 350–500 nm for a series of standard solutions by linear least-squares regression. This method used information from the absorption spectra of U(VI)–nitrous acid–nitric acid solutions to determine U(VI), nitrous acid and nitric acid. In the range of 0.95–74.1 g/L U(VI), 5 × 10^?4–2 × 10^?3 mol/L nitrous acid and 3–5 mol/L aqueous nitric acid solution, the measuring precision for determination of U(VI), nitrous acid and nitric acid was 0.46, 4.09, and 0.68 % respectively. In the solution of 30 % TBP–kerosene, the measuring precision for determination of U(VI) and nitrous acid was 0.42 and 4.2 % respectively in the range of 0.95–74.1 g/L U(VI) and 5 × 10^?4–2×10^?3 mol/L nitrous acid. The spectrophotometric method can be valuable for monitoring and controlling of both species in PUREX process operation, thanks to its simplicity, efficiency and accuracy.     

Synergistic extraction of uranium(VI) from nitric acid solution by mixture of DMHMP and DOSO in benzene

Solvent extraction of uranyl nitrate in nitric acid medium with the binary system of DMHMP and DOSO has been investigated. It was found that synergistic effect occurs during the extraction of uranyl nitrate with benzene solution of DMHMP and DOSO, the binary species extracted UO₂ (NO₃)₂·DMHMP·DOSO has been confirmed. From the data the equilibrium constants have been determined.